1. Field of the Invention
The present invention relates to a fuel injection apparatus for an internal combustion engine for controlling a fuel injection quantity on the basis of data corresponding to CO (carbon monoxide) regulating correction quantities. More particularly, the present invention is concerned with a fuel injection apparatus for an internal combustion engine in which data input processing and data search processing are moderated while the amount of data to be held is decreased for thereby realizing implementation of the fuel injection apparatus at a low cost without impairing accuracy of the fuel injection control.
2. Description of Prior Art
In general, in the fuel injection apparatus for the internal combustion engine, the fuel injection quantity is arithmetically determined or calculated in dependence on the operation state of the internal combustion engine determined on the basis of the detection information outputted from various type of sensors. In that case, with a view to decreasing the discharge quantity of CO (carbon monoxide) contained in the engine exhaust gas, a basic fuel injection quantity is additively corrected with map data (CO regulating correction quantity data) which also depends on the operation state of the engine, whereby the fuel injection quantity is optimally adjusted or regulated.
Through the procedure mentioned above, influence of dispersion of the engine and the various types of sensors can be canceled out or compensated for, and thus it becomes possible to control the fuel injection quantity with high accuracy in conformance with the operation state of the engine.
For better understanding of the concept underlying the present invention, description will first be made of a conventional fuel injection apparatus for an internal combustion engine known heretofore. FIG. 4 of the accompanying drawings is a block diagram showing schematically and generally a conventional fuel injection apparatus for the internal combustion engine.
Referring to FIG. 4, the internal combustion engine (hereinafter also referred to simply as the engine) is provided with various types of sensors for detecting the operation state of the engine, as generally designated by a reference numeral 10, a control unit which may be constituted by a microprocessor or microcomputer 20 for arithmetically determining engine control quantities in dependence on the operation states of the engine, and a fuel injector 30 for injecting fuel into the engine.
The various types of sensors 10 include a throttle position sensor 11 for detecting an opening degree Th of a throttle valve (not shown) and a crank angle sensor 12 for detecting a rotation number or speed Ne [rpm] of the engine. The throttle opening degree Th and the rotation speed Ne [rpm] of the engine are inputted into the microcomputer 20 together with other sensor information indicative of the operation state of the engine.
The microcomputer 20 incorporates an EEPROM (Electrically Erasable and Programmable ROM) 21 as a storage means for storing or holding therein the results of the arithmetic operations (i.e., various control quantities).
Further, connected to the microcomputer 20 is an external terminal unit 40 which may be constituted by a computer so that bi-directional data communication can be effectuated between the external terminal unit 40 and the microcomputer 20 through the medium of a serial communication interface.
Set previously in the EEPROM 21 which belongs to the microcomputer 20 are basic fuel injection quantities in correspondence to the operation states, respectively, of the engine.
In this conjunction, it should be added that the EEPROM 21 also serves as a data map means for holding individual data (described later on) corresponding to the CO regulating correction quantities in a plurality of areas as determined in dependence on the throttle opening degree Th and the engine rotation speed Ne [rpm].
The microcomputer 20 is comprised of a basic fuel injection quantity arithmetic means for calculating (i.e., arithmetically determining) basic quantity of fuel injected from the fuel injector 30 on the basis of the operation state of the engine and a correcting arithmetic means for arithmetically determining the fuel injection quantity by additively correcting the basic fuel injection quantity with the data corresponding to the relevant area of the EEPROM 21.
The microcomputer 20 is so arranged as to reference the data values stored in the EEPROM 21 on the basis of the operation state determined from the output of the various types of sensors 10 to thereby arithmetically determine the final fuel injection quantity.
Next, referring to FIGS. 5 to 7 of the accompanying drawings together with FIG. 4, description will be directed to the fuel injection quantity control operation carried out by the conventional fuel injection apparatus for the internal combustion engine.
FIG. 5 is a flowchart for illustrating a fuel injection quantity calculation routine executed by the microcomputer 20.
Further, FIG. 6 is a view for illustrating a data map of the CO regulating correction quantity known heretofore, and FIG. 7 is a view for illustrating data values at individual points based on the data map shown in FIG. 6.
Referring to FIGS. 6 and 7, data D1 to D16 for the CO regulating correction quantity are arrayed in a three-dimensional data map with the throttle opening degree Th and the engine rotation speed Ne [rpm] being used as parameters, wherein sixteen areas determining the individual data D1 to D16, respectively, result from division by four throttle opening degrees Th1 to Th4 on one hand and four engine rotation speeds Ne1 to Ne4 on the other hand.
At this juncture, it is noted that the relation among the throttle opening degrees Th1 to Th4 is given by
Th1 less than Th2 less than Th3 less than Th4.
Further, relation among the engine rotation numbers or speeds Ne1 to Ne4 is given by
Ne1 less than Ne2 less than Ne3 less than Ne4.
In more concrete, the throttle opening degrees and the engine rotation speeds may be set, by way of example, as follows:
Th1=10 [deg]
Th2=12 [deg]
Th3=30 [deg]
Th4=32 [deg]
Ne1=3000 [rpm]
Ne2=3200 [rpm]
Ne3=4500 [rpm]
Ne4=4750 [rpm]
In the exemplary case mentioned above, in the area for the data D1 shown in FIG. 6, the throttle opening degree Th is not greater than Th1 [deg] with the engine rotation speed Ne being not greater than Ne1 [rpm]. This area thus corresponds to an idling and low-speed operation range.
Further, in the areas corresponding to the data D4, D8 and the like, the engine rotation speed is not higher than Ne4 [rpm] and represent a high-speed operation range.
Further, the data D2, D3 and the like are represented by point data values (see FIG. 7) in point regions determined by the throttle opening degree and the engine rotation speed. In this case, the data value within a range of the engine rotation speeds [rpm] Ne2 to Ne3 can be determined through a linear interpolation calculation between two points.
Furthermore, in FIG. 7, individual CO regulating correction quantity data values exist at the prints (grids), respectively, which are determined by the throttle opening degrees Th1 to Th4 and the engine rotation speeds [rpm] Ne to Ne4, respectively.
Now referring to FIG. 5, the basic fuel injection quantity and the various correcting values for the basic fuel injection quantity are arithmetically determined or calculated on the basis of the input information from the various types of sensors 10 (indicating the engine operation state) in a step S1, which is then followed by a step S2 where the CO regulating correction quantity conforming to the throttle opening degree Th and the engine rotation speed Ne [rpm] are arithmetically determined.
In this conjunction, it is to be mentioned that the CO regulating correction quantity can be determined by referencing the data value of the CO regulating correction quantity map (map data stored in the EEPROM 21) (FIG. 6) in dependence on the throttle opening degree Th and the engine rotation speed Ne [rpm] (i.e., with the throttle opening degree Th and engine rotation speed Ne being used as parameters).
Next, the value resulting from addition of the CO regulating correction quantity to the basic fuel injection quantity is multiplied by the relevant various correcting values, the resulting value being then outputted as the final fuel injection quantity (step S3), whereupon the processing routine shown in FIG. 5 comes to an end.
In succession, the microcomputer 20 outputs the control value corresponding to the fuel injection quantity to thereby drive the fuel injector 30.
Next, description will be made of the data input processing generally executed upon shipping of the fuel injection apparatus for the internal combustion engine.
Upon shipping of the engine, the fuel injection quantity containing the CO regulating correction quantity (the value arithmetically determined or calculated on the basis of the current throttle opening degree Th and engine rotation speed Ne [rpm]).
In succession, in the engine operation state mentioned above, the CO discharge quantity contained in the exhaust gas is measured by means of a CO concentration measuring instrument, whereon the map data values of the CO regulating correction quantities in the individual areas are so altered or modified that the optimum air-fuel ratio can be realized. By storing the optimum CO regulating correction quantity data in the EEPROM 21, the CO regulating correction quantities are altered. In other words, the precision or accuracy of fuel injection control is improved by altering or modifying the fuel injection quantity.
In that case, alteration or modification of the CO regulating correction quantities (data values) stored in the EEPROM 21 as well as writing there of is performed by connecting the external terminal unit 40 to the microcomputer 20 by way of a serial communication interface.
As can be appreciated from the above, the conventional fuel injection apparatus for the internal combustion engine suffers a problem that the EEPROM 21 must necessarily be implemented with a large capacity because for all the points (grids) comprised of the throttle opening degrees Th1 to Th4 at the four points along the ordinate and the engine rotation speeds Ne1 to Ne4 at the four points along the abscissa, all the sixteen data D1 to D16 have to be held in the EEPROM 21.
Furthermore, because it is required to adjust the air-fuel ratio and rewrite the data in all the areas when the data for the CO regulation are altered, lots of time is taken for the processings involved.
In the light of the state of the art described above, it is an object of the present invention to provide a fuel injection apparatus for an internal combustion engine for which the data input processing and the data search processing and hence the cost can be reduced by decreasing the amount or number of the data to be held without impairing the precision or accuracy of the fuel injection control.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a fuel injection apparatus for an internal combustion engine, which apparatus includes various types of sensors for detecting operation state of the internal combustion engine, a control unit for arithmetically determining a fuel injection quantity to be injected into the internal combustion engine in dependence on the engine operation state, and a fuel injector for injecting the fuel into the internal combustion engine in conformance with the fuel injection quantity determined arithmetically. In the fuel injection apparatus mentioned above, the control unit is comprised of a basic fuel injection quantity arithmetic means for arithmetically determining a basic fuel injection quantity in dependence on the engine operation state, a data map means for holding a plurality of data for determining a regulating correction quantity in dependence on specific parameters of the engine operation state, and a correcting arithmetic means for determining the fuel injection quantity by correcting the basic fuel injection quantity with the data. The data map means mentioned above includes a plurality of areas for holding the data, wherein the plurality of areas have intermediate areas holding no data between two adjacent areas. The correcting arithmetic means mentioned above includes a map search means for arithmetically determining interpolation data corresponding to the intermediate area through interpolation arithmetic based on the data stored in the two adjacent areas, respectively. The fuel injection quantity corresponding to the intermediate area is determined by correcting the basic fuel injection quantity with the interpolation data.
The fuel injection apparatus according to the present invention described above, the number of data to be held can significantly be decreased, allowing the apparatus to be implemented at a low cost without impairing the fuel injection control accuracy.
In a preferred mode for carrying out the invention, the data for the fuel injection apparatus correspond to a carbon monoxide regulating correction quantity for reducing the discharge quantity of carbon monoxide contained in the exhaust gas of the internal combustion engine. As the specific parameters mentioned previously, a throttle opening degree and an engine rotation speed [rpm] of the internal combustion engine are employed. The data map means is so designed as to hold the carbon monoxide regulating correction quantities corresponding to the throttle opening degree and the engine rotation speeds in the form of a three-dimensional data map.
In another preferred mode for carrying out the invention, the correcting arithmetic means of the fuel injection control apparatus is so designed as to arithmetically determine the fuel injection quantity by adding the data or alternatively the interpolation data to the basic fuel injection quantity.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.